Test ready-mixed concrete in accordance with the following methods: The purpose of the opening statement in Section 15.1 is to prohibit the reporting of test results or rejection of concrete on the basis of any test method not included in the subsections of 15.1. Each of these test methods has prescribed equipment and procedures to produce as much uniformity and repeatability as possible in the test results. Other test methods or deviations from the prescribed test methods or practice are not permitted.